The present invention relates to a plastic pattern casting system and particularly to an EPS (Expanded Polystyrene) plastic foam pattern casting system for production of widely different components.
In manufacture of products, machines and mechanisms individual parts may be formed in various processes. Thus, certain parts may be machined or processed from stock material, while other parts may be formed of a cast metal. Various components and parts for various machines and products are more economically and easily formed as cast metal members. In the machining art, a production line may necessarily process a number of different components and parts. To adapt the production lines to various products, machine subunits have been developed for interpositioning into a production line so as to adapt the line to various manufacturing or casting processes and sequences.
The conventional method of forming cast parts involves various sand casting processes. A more recent development in the commercial field involves a foam pattern casting process in which a foam pattern is formed of expandable polystyrene plastic by known molding techniques. The formed pattern is embedded in a loose, unbonded sand mass with a sprue projecting upwardly out of the sand mass. Hot metal is introduced into the sand mass through the sprue and serves to vaporize the cavity defining pattern and fills the void, thereby reproducing of the foam molded pattern. The foam casting process include many advantages in cost reduction and simplification of the manufacturing process.
The scheduling of the foam casting process follows the same basic approach as that used in conventional sand casting. The foam patterns are produced in batches for a pouring run. The patterns are staged for the pouring run and inserted sequentially into the pouring line so that all the parts of a given configuration or size are produced together or in sequence. Upon completion of the run of such a part, the system is reorganized for the production of a different part
Generally, any given production run is set to produce the part both for a particular demand as well as for inventory. Although such conventional practice has been widely adapted and satisfactorily adapted for mass production, the system may prevent maximum efficiency and usage of the manufacturing facility. Thus, even though a given part may be needed on a priority basis, a system established and running a relatively large production run of some other component or part will normally continue to complete that run as a practical consideration because of the time and cost involved to change or interrupt the system operation. This results in various manufacturers and/or users establishing a relatively large inventory of various parts to avoid the delays and costs associated with interrupting the on-line casting process. The casting process could use several subassemblies for interposing of such units in the various parts of production casting line. This of course would require significant fixed cost and special apparatus for interconnecting of various units into a casting line. To the best knowledge of the present inventor, such modified systems have not been used and the conventional approach is a standard procedure in the casting business.
In summary, the foundry of today, even with the high production machines which have been developed, is essentially a batch process. The reason for using the batch process approach is that the change over downtime and/or the difficulty of maintaining control of quality makes other processes uneconomical.
There therefore exists a significant and substantial need for an "on-demand" casting process in which the casting line is readily adapted to interposing of various casting schedules, and varying of the casting schedules to provide maximum efficiency of the overall manufacturing system.